Field of the Invention
The invention relates in particular to the filed of multichannel electrooptical data transmission connections and pertains to an electrooptical module with at least one electrooptical converter.
Within the scope of the present invention, the term "electrooptical converter" is understood to mean both a transmitting and a receiving element (such as light-emitting diodes, surface-emitting laser diodes, or photodiodes). The optically active surface region or regions of the converter, that is light-emitting zones for a transmitter and light-sensitive zones for a receiver, will be referred to below by the general term "optically active zones".
An especially critical region in module construction in terms of the capacity and coupling efficiency of a module is a coupling point between the converter and an injection region of an optical fiber (optical waveguide) serving the purpose of guiding light. In the case of multichannel modules, a number of coupling points corresponding to the number of channels is necessary. In principle, such coupling regions must be protected against external influences, and in particular against condensing moisture from the air and temperature changes, for example.
One protection possibility employed heretofore is a hermetically sealed encapsulation of the module in a comparatively complex and expensive hermetic housing. In an individual encapsulation of the coupling gap, that is known in principle, for instance, from Published European Patent Application 0 466 975 A1 or German Published, Non-Prosecuted Patent Application DE 43 23 828 A1, which uses a covering or casting composition, considerable problems arise because of component geometry and component length, especially in multichannel modules with converters having a plurality of optically active zones. That occurs as a consequence of different thermal expansion behaviors of the individual components, especially the converter and the optical wave guide array to be coupled. Another problem area in multichannel high-power modules is that for triggering the converters (transmitters) or further processing of the converter signals (receivers), the integrated electrical circuits which are required for that purpose, if high operating frequencies are to be achieved, should be disposed as much as possible in the immediate vicinity of the converter components and connected with short bonding wires. The integrated electrical circuits which are used for that purpose as a rule are light-sensitive and must therefore be protected against the entry of outside light or against being exposed to stray light from the converter.
No satisfactory overall solution has been disclosed heretofore for those complex and specific protection requirements of the coupling gap on one hand and of the electrical circuit on the other hand within the smallest possible space. In protection materials that differ in composition or structure and are optimized in terms of their optical properties, it proves to be problematic to lead the bonding wires through, because of the different thermal properties of the materials.